1. Field of the Invention
The present invention generally relates to a lock-up device which utilizes a ball and cam arrangement to interlock two members. The interlocked members include ball engagement surfaces which are concave so that a substantial portion of the ball surface is in contact with the engagement surfaces. More particularly, the invention relates to a firearm having a ball and cam-type lock-up mechanism to withstand high chamber pressure when the firearm is discharged and also to store inertial force from recoil which is utilized by linear reaction to unlock the mechanism and cycle ammunition, without rotational movement. It should be noted that the word firearm is being used in this application to mean any device which discharges a projectile by use of an explosive charge.
2. Description of the Background Art
Prior art firearms utilize a barrel mounted gas release system operatively connected to the bolt for the release of lock-up by rotation of interlocking lugs and to move rearwardly whereby loading of ammunition may automatically be carried out after a first round is fired. Such gas cycling methods require a complex means of connection to the bolt and require exposed locking surfaces specifically located with the bolt, which are subject to stoppage by debris, and are difficult to manufacture, especially when interchangeability of parts are required such as for organizational or departmental use. Therefore, it is desirable to have a mechanism which does not require specific location in the firearm, a gas connecting means, or rotating locking surfaces, and can be a sealed universal unit which is easily replaceable and not subject to interruption by debris, which would improve the reliability, manufacture and maintenance of the firearm.
The present invention utilizes an improved ball and cam lock-up arrangement heretofore unknown in the prior art. However, ball and cam locking devices are known for use in locking cylindrical members together.
A known locking device is disclosed in U.S. Pat. No. 3,507,528 to Desmarchais. Desmarchais '528 shows a ball-type locking device with an intermediate disengagement member. However, the ball contact surfaces contact the ball in a point engagement which results in distortion of the locking surfaces and the balls if to large a force is exerted on the locking device.
Another known locking device is disclosed in U.S. Pat. No. 3,761,117 to Shendure. The Shendure patent is also illustrative of the primary deficiencies in current ball/cam lock-ups. Namely, a lack of necessary surface contact between the ball and locking surfaces to prevent deformation under extreme loads which tends to inhibit or prohibit unlocking of the device. The Shendure device does provide a curved locking surface, but this surface is not substantially equal to that of the ball. The combination of surfaces in Shendure will only achieve essentially a point contact on the locking surface and a line contact in the frusto-conical ball retention member.